AR lower in non 223/556 build

[Melnic]

If you buy a post 2013 AR lower but mate it to a non 223/556 upper (say 9mm or 300blk)
Does that make it banned or does it have to be HBAR profile to be non banned?

 

[l730dc]

I did not see anything in the bill that said anything about caliber... so without a specific exemption for caliber.. ide say not to.. only exemptions for an ar15 rifle is hbar

 

[outrider58]

If you buy a post 2013 AR lower but mate it to a non 223/556 upper (say 9mm or 300blk)
Does that make it banned or does it have to be HBAR profile to be non banned?

9mm and 300 AAC barrels are, by their nature, essentially h-bars so no problem there.